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Last modified
1/26/2010 12:36:04 PM
Creation date
10/11/2006 11:01:55 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8240.300.03
Description
San Juan River - Recovery Implementation Program - General Info
Basin
San Juan/Dolores
Water Division
7
Date
3/7/1996
Author
Fish and Wildlife Se
Title
Biological Opinion
Water Supply Pro - Doc Type
Biological Opinion
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<br />" <br /> <br />Mr. Calvin Joyner <br /> <br />9 <br /> <br />c, <br />o <br />\.) <br />i\.,"l <br />tJ1 <br />~ <br /> <br />Only two Colorado squawfish confirmed spawning sites, as defined in the <br />Colorado Squawfish Recovery Plan, have been located in the Upper Basin: river <br />mile 16,5 of the Yampa River and river mile 156.6 of the Green River. These <br />areas have the common characteristics of coarse cobble or boulder substrates <br />forming rapids or riffles associated with deeper pools or eddies. It is <br />believed that a stable, clean substrate is necessary for spawning and <br />incubation. Substrates are swept clean of finer sediments by high flows <br />scouring the bed prior to the spawning period. <br /> <br />O'Brien (1984) studied the hydraulic and sediment transport dynamics of the <br />cobble bar within the Yampa River spawning site and duplicated some of its <br />characteristics in a laboratory flume study. Based on field observations, he <br />reported: <br /> <br />"On the rising limb of the hydrograph, sands are deposited in the <br />cobble interstices. These sands are interchanged between the bed <br />and the suspended zone for discharges less than bankfull. <br />Depending on the supply-capacity relationship, either deposition <br />or scour could be occurring, When the cobbles move, the sand, of <br />course, is washed from the interstices and may be completely <br />removed from around the cobbles. Rearrangement of the cobbles <br />will result in more stability of the armor layer. On the falling <br />limb, the armor layer becomes a trap for sands until finally, the <br />sand reservoir is again filled. Without cobble movement, sand <br />will be scoured only to a depth of one-half to one median cobble <br />diameter below the cobble bed surface," <br /> <br />In the flume experiments, the sand level was observed approximately 0.50 to <br />1 cobble diameter below the surface of the cobble bed, which compared to field <br />observations of sand depth at approximately 0.50 to 1 median cobble diameter. <br />O'Brien reported a cobble size range of 50-100 mm with a median size of 75 mm <br />at the spawning site. Milhous (1982) proposes discharges of approximately <br />one-half that required to initiate cobble movement will be capable of <br />extracting sands and fines from the cobble substrate. Thus, after the supply <br />of sand diminishes, flows of sufficient magnitude and duration are required to <br />scour the cobble bed in preparation for spawning and incubation. <br /> <br />Razorback Sucker <br /> <br />Historical and Current Distribution <br /> <br />The razorback sucker, an endemic species unique to the Colorado River Basin, <br />was historically abundant and widely distributed within warmwater reaches <br />throughout the Colorado River Basin. Historically, razorbacks were found in <br />the main stem Colorado River and major tributaries in Arizona, California, <br />Colorado, Nevada, New Mexico, Utah, Wyoming, and in Mexico (Ellis 1914; <br />Minckley 1973). Bestgen (1990) reported that this species was once so <br />numerous that it was commonly used as food by early settlers, and further, <br />that commercially marketable quantities were caught in Arizona as recently as <br />1949, In the Upper Basin, razorback suckers were reported in the Green River <br />to be very abundant near Green River, Utah, in the late 1800's (Jordan 1891). <br />An account in Osmundson and Kaeding (1989) reported that residents living <br />
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